1 /* 2 * Copyright (C) 2012 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.google.common.hash; 16 17 import static com.google.common.base.Preconditions.checkArgument; 18 import static com.google.common.base.Preconditions.checkNotNull; 19 20 import com.google.common.base.Supplier; 21 22 import java.io.Serializable; 23 import java.util.zip.Checksum; 24 25 /** 26 * {@link HashFunction} adapter for {@link Checksum} instances. 27 * 28 * @author Colin Decker 29 */ 30 final class ChecksumHashFunction extends AbstractStreamingHashFunction implements Serializable { 31 32 private final Supplier<? extends Checksum> checksumSupplier; 33 private final int bits; 34 private final String toString; 35 ChecksumHashFunction(Supplier<? extends Checksum> checksumSupplier, int bits, String toString)36 ChecksumHashFunction(Supplier<? extends Checksum> checksumSupplier, int bits, String toString) { 37 this.checksumSupplier = checkNotNull(checksumSupplier); 38 checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits); 39 this.bits = bits; 40 this.toString = checkNotNull(toString); 41 } 42 43 @Override bits()44 public int bits() { 45 return bits; 46 } 47 48 @Override newHasher()49 public Hasher newHasher() { 50 return new ChecksumHasher(checksumSupplier.get()); 51 } 52 53 @Override toString()54 public String toString() { 55 return toString; 56 } 57 58 /** 59 * Hasher that updates a checksum. 60 */ 61 private final class ChecksumHasher extends AbstractByteHasher { 62 63 private final Checksum checksum; 64 ChecksumHasher(Checksum checksum)65 private ChecksumHasher(Checksum checksum) { 66 this.checksum = checkNotNull(checksum); 67 } 68 69 @Override update(byte b)70 protected void update(byte b) { 71 checksum.update(b); 72 } 73 74 @Override update(byte[] bytes, int off, int len)75 protected void update(byte[] bytes, int off, int len) { 76 checksum.update(bytes, off, len); 77 } 78 79 @Override hash()80 public HashCode hash() { 81 long value = checksum.getValue(); 82 if (bits == 32) { 83 /* 84 * The long returned from a 32-bit Checksum will have all 0s for its second word, so the 85 * cast won't lose any information and is necessary to return a HashCode of the correct 86 * size. 87 */ 88 return HashCode.fromInt((int) value); 89 } else { 90 return HashCode.fromLong(value); 91 } 92 } 93 } 94 95 private static final long serialVersionUID = 0L; 96 } 97